Fix percent sign in quoted attribute values being treated as comment

[dereuromark]

Summary

• Fixes bug where % inside quoted attribute values (e.g., title="100% done") was incorrectly treated as a comment marker
• The previous regex-based removeComments() stripped all content between % markers without considering quotes
• Rewrites removeComments() to be quote-aware by scanning character-by-character
• Quoted strings are now copied verbatim, preserving literal % characters inside them

Before:

Input:  [text]{title="100% done"}
Output: <p><span>text</span></p>  ← title attribute was stripped

After:

Input:  [text]{title="100% done"}
Output: <p><span title="100% done">text</span></p>  ✓

Verified against reference JS implementation (@djot/djot).

Changes

• src/Parser/Utility/AttributeParser.php: Rewrite removeComments() to be quote-aware
• tests/TestCase/Parser/AttributeParserTest.php: Add 7 tests for percent signs in quoted values

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.61%. Comparing base (274c09f) to head (27fe8aa).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #109      +/-   ##
============================================
+ Coverage     93.57%   93.61%   +0.03%     
- Complexity     2316     2328      +12     
============================================
  Files            79       79              
  Lines          6134     6168      +34     
============================================
+ Hits           5740     5774      +34     
  Misses          394      394              

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